Anode assembly for electrolytic cells

ABSTRACT

AN ANODE ASSEMLY SUITABLE FOR USE IN A CELL FOR THE ELECTROLYSIS OF ALKALI METAL HALIDE SOLUTIONS WHICH COMPRISES (1) A PLURALITY OF SUBSTANTIALLY PARALLELLY DISPOSED PLATELIKE ELECTRODES, EACH OF WHICH HAVE A PAIR OF SUBSTANTIALLY PARALLEL PLATE-LIKE FACES, SAID ELECTRODES HAVING AN OUTER SURFACE OF A VALVE METAL, CO COATED WITH AN ELECTRICALLY ACTIVE MATERIAL, EACH OF SAID ELECTRDOES FURTHER HAVING TWO SETS OF SUBSTANITALLY OPPOSITELY DISPOSED SIDES, (2) A PLURALITY OF MOUNTING MEMBERS, ONE OF SAID MOUNTING MEMBERS BEING SECURED TO EACH FACE OF EACH ELECTRODE AT A POINT ADJACENT ONE SIDE OF ONE OF SAID SETS OF SIDES AND EXTENDING BETWEEN THE TWO OPPOSITELY DISPOSED SIDES OF SAID OTHER SET, SAID MOUNTING MEMBERS EACH BEING SUBSTANTIALLY PERPENDICULAR TO THE FACE OF THE ELECTRODE OT WHICH IT IS SECURED AND EXTENDING THEREFROM A DISTANCE WHICH IS ABOUT ONE-HALF THE DESIRED DISTANCE BETWEEN TWO ADJACENT ELECTRODES IN THE FINAL ANODE ASSEMBLY SAID MOUNTING MEMBER ON THE FACE OF ONE ELECTRODE BEING SECURED TO THE CORRESPONDING MOUNTING MEMBER ON THE FACE OF AN ADJACENT ELECTRDOE SO AS TO FORM A UNITARY ANODE ASSEMBLY AND   (3) ELECTRIAL CONNECTION MEANS ON SAID PLATE-LIKE ELECTRODES, ADJACENT THE SAID MOUNTING MEMBERS.

Sept. 25, 1973 w. w, RUTHEL ETAL 3,761,384

ANODE ASSEMBLY FOR ELECTROLYTIC CELLS Filed June 30, 1971 7 7 aaaap 5 aqa 5 o oo United States Patent US. Cl. 204-288 6 Claims ABSTRACT OF THE DISCLOSURE An anode assembly suitable for use in a cell for the electrolysis of alkali metal halide solutions which comprises (l) a plurality of substantially parallelly disposed platelike electrodes, each of which have a pair of substantially parallel plate-like faces, said electrodes having an outer surface of a valve metal, coated with an electrically active material, each of said electrodes further having two sets of substantiall oppositely disposed sides,

(2) a plurality of mounting members, one of said mounting members being secured to each face of each elec trode at a point adjacent one side of one of said sets of sides and extending between the two oppositely disposed sides of said other set, said mounting members each being substantially perpendicular to the face of the electrode to which it is secured and extending therefrom a distance which is about one-half the desired distance between two adjacent electrodes in the final anode assembly, said mounting member on the face of one electrode being secured to the corresponding mounting member on the face of an adjacent electrode so as to form a unitary anode assembly and (3) electrical connection means on said plate-like electrodes, adjacent the said mounting members.

This invention relates to an improved anode assembly and more particularly it relates to an anode assembly which is suitable for use in a cell for the electrolysis of alkali metal halide solutions.

In recent years, considerable development work has been done on metallic or dimensionally stable electrodes, particularly for use as anodes in electrolytic cells for the production of chlorine, hypochlorites or chlorates by the electrolysis of alkali metal chloride solutions. Although many electrodes of this type have been proposed, one of the most promising has been an electrode having a base ofa so-called valve metal, such as titanium, and an electrically active coating of a noble metal, noble metal alloy or noble metal oxide, such as platinum, ruthenium oxide, or the like.

One of the problems which has been encountered with electrodes of this type has been that of mounting them so as to form the desired anode assembly for the electrolytic cell. With many of the mounting means which have heretofore been proposed, difficulties have been encountered in obtaining sufficient rigidity of the overall anode assembly so as to maintain the desired spacings between the anodes and cathodes. Additionally, because of the need for providing an electrical connection to the anode which is external of the cell, problems have also been encountered with the sealing means for preventing leakage of electrolyte, with resulting corrosion of the electrical connections and consequent adverse effects on the operating voltages of the cell.

It is, therefore, an object of the present invention to provide an improved, unitary anode assembly of metal or dimensionally stable electrodes for use in electrolytic cells for the electrolysis of alkali metal halide solutions.

3,761,384 Patented Sept. 25, 1973 A further object of the present invention is to provide an improved anode assembly which is relatively simple to manufacture and overcomes the problems of alignment and sealing which have h'eretofore been encountered with anodes of this type.

These and other objects of the present invention will become apparent to those skilled in the art from the description of the invention which follows.

In the drawings, which are attached hereto and form a part hereof, FIG. 1 is a plan view of the anode assembly of the present invention and FIG. 2 is a perspective view of the anode assembly of the present invention.

Pursuant to the above objects, the present invention includes an anode assembly, suit-able for use in a cell for the electrolysis of alkali metal halide solutions, which comprises (1) a plurality of substantially parallelly disposed platelike electrodes, each of which have a pair of substantially parallel, plate-like faces, said electrodes having an outer surface of a valve metal selected from titanium, tantalium and niobium, coated with an electrically active material selected from noble metals, noble metal alloys, noble metal oxides and mixtures thereof, said noble metals being selected from platinum, palladium,

ruthenium, rhodium and irridium, each of said electrodes having two sets of substantially oppositely disposed sides,

(2) a plurality of mounting members, said mounting members being disposed between said electrodes and secured to the oppositely disposed faces of adjacent electrodes at a point adjacent one side of one of said sets of sides of said electrode and extending between the two oppositely disposed sides of said other set of sides, said mounting members being substantially perpendicular to the face of the electrodes to which they are secured so as to maintain said electrodes in a substantially parallel relationship and form with said electrodes a unitary anode assembly and (3) electrical connection means on said plate-like electrodes, adjacent the said mounting members.

It has been found that these anode assemblies of the present invention may be easily fabricated and form a unitary structure in which the proper alignment of the electrode is maintained and which provides an electrical connection to these electrodes which is outside the electrical cell in which the assembly is used.

More specifically, the anode assembly of the present invention may be utilized in various cells for the electrolysis of alkali metal halide solutions, for the production of chlorine, hypochlorites, chlorates, or the like. Such cells may be of the type in which the anodes are mounted in the bottom of the cell, on the side of the cell, or even on the top of the cell. This anode assembly has, however, been found to be particularly adapted for use in side mounted or side entry type cells, so that particular reference hereinafter will be made to this type of use. This is not, however, to be taken as a limitation on the present anode assembly since it may be readily adapted for use in other types of cells as well.

The electrodes used in the anode assembly of the present invention are formed of a valve metal and coated with an electrically active material. The valve metals which may be used include titanium, tantalum and niobium, with titanium being preferred. Additionally, the electrically active materials with which the titanium is coated include noble metals, noble metal alloys, noble metal oxides and mixtures of these, with the noble metals being selected from platinum, palladium, ruthenium, rhodium and iridium. Of these, the preferred electrically active coatings are those which contain ruthenium oxide. Additionally, in a most preferred embodiment, these electrodes have an inner core of a material which is more electrically conductive than the valve metals, such as titanium. Exemplary of such electrically conductive materials which may be used for this core are aluminum, copper, iron and the like. Exemplary of a particularly preferred electrode of this latter type is that described in a copending application filed of even date herewith and identified as Ser. No. 158,414.

The electrodes disclosed in this patent application are multi-layered, plate-like structures which are formed of an inner plate of an electrically conductive material, such as aluminum, copper or iron. This inner plate is encapsulated within two outer plates of a valve metal, such as titanium, tantalum or niobium. The outer plates are discontinuously bonded to the inner plate by effecting a fusion of that portion of the inner plate at the bond to the outer plate, with no substantial fusion of the outer plate. The exterior of these outer plates is covered with an electrically active coating of a noble metal, noble metal alloy, noble metal oxide or mixtures of these. Such electrodes are particularly preferred for the anode assembly of the present invention in that they may be fabricated in a variety of appreciably larger sizes than solid titanium electrodes, wtihout sacrifice of electrical characteristics. The disclosure of this copending application is hereby incorporated by reference in the present application as being descriptive of the preferred embodiment of the electrodes used in the present anode assembly.

It is to be appreciated, however, that although the preferred electrodes are those of the type described in the above indicated copending application, the electrodes which are suitable for use in the present anode assemblies are not limited to this specific type. In general, the electrodes used preferably are substantially rectangular in shape, having two sets of substantially oppositely disposed sides and a pair of substantially parallel plate-like faces. The electrodes may be formed of titanium sheets or plates, either with or without the preferred inner core of aluminum, and having an exterior coating of the electrically active material, such as one containing the noble metal oxides. Additionally, the electrode may be formed with titanium screen or mesh, expanded titanium metal or other perforated or foraminous titanium, rather than sheets or plates of titanium. These may be used as such or in combination with plates or sheets and may also include a core of a more conductive metal, such as aluminum. Where such foraminous structures are used the configuration will be one to which mounting members can be secured in the manner described hereinafter. Typically, this will include a sheet or plate to which both the mounting members and the foraminous material are secured.

The present anode assembly contains a plurality of these electrodes, disposed in a substantially parallel relationship to each other. The number and size of the electrodes in the assembly may vary widely, depending upon the particular electrolytic cell in which the assembly is to be used. Similarly, the spacing between the parallelly disposed electrodes will also vary depending upon the nature of the cathode which is to be disposed between the electrodes. Thus, with the electrode assembly of the present invention, considerable variations are possible to accommodate a variety of different operating conditions, without encountering undesirably large voltage drops.

Disposed between the parallel electrodes are a plurality of mounting members. These mounting members are secured to the oppositely disposed faces of the adjacent electrodes so as to maintain the electrodes in a substantially parallel relationship and form with them the unitary anode assembly of the present invention. These mounting members are secured to the electrodes faces at a point which is adjacent one side of one of the sets of sides of the electrode and extends between the oppositely disposed sides of the other set of sides. The mounting members are substantially perpendicular to the face of the electrodes to which they are secured and form One wall of the electrolylic cell in which the anode assembly is mounted, most preferably, a side wall. In a most preferred embodiment, one mounting member is secured to each face of each electrode, at the position described above, and the mounting members extend, substantially perpendicularly, from the face of the electrode to which it is secured a distance which is about one-half the desired distance between two adjacent electrodes in the final anode assembly. The mounting member on the face of one electrode is then secured to the corresponding mounting member on the face of the adjacent electrode, to secure the electrodes in the final unitary anode assembly and form one wall of the electrolytic cell.

The mounting members may be of various configurations, as will be described in more detail hereinafter. The mounting members may be formed of any suitable materials which will provide the necessary support for the electrodes in the anode assembly and which will withstand the corrosive effective of the environment of which they are used. Preferably, the mounting members are made of metal and, most preferably, are made of the same valve metal as the electrode. In this manner, not only is the maximum corrosion resistance obtained, without the need for a corrosion resistant coating, but, additionally, corrosion as a result of galvanic action between two dissimilar metals is avoided.

The mounting members may be secured to the electrode faces, and to each other in the case of the most preferred embodiment, in any convenient manner. In many instances, it has been found to be preferred to secure these elements by welding although other methods such as soldering, brazing, and the like, may also be used. The important factor in securing the mounting members to the electrodes and to each other is that in whatever method is used, sufiicient rigidity is imparted to the final anode assembly as to maintain the desired spaced relationships and, further, that the joint formed is subjected to a minimum of corrosion by the environment in which the cell is used.

The electrodes in the anode assembly of the present invention are further provided with a suitable electrical connection. Desirably, this connection is positioned adjacent the mounting members and most preferably, on the side of the mounting members which is exterior of the cell. Any suitable electrical connection for bringing the operating current into the cell may be used, as are known to those in the art. Additionally, the anode assembly is provided with means for mounting the assembly in the electrical cell in which it is to be used. The specific configuration of such mounting means will, of course, depend upon the particular type of electrolytic cell in which the anode assembly is to be used.

Referring now to the drawings, FIG. 1 is a plan view of the anode assembly of the present invention, while FIG. 2 is a perspective view of this assembly. As is shown in these figures, the anode assembly is comprised of a series of electrodes 1, each of which has a pair of substantially parallel, plate-like faces 9. A plurality of mounting members 3 are secured to the faces 9 of the electrodes 1 so as to support the electrodes, maintaining them in a substantially parallel relationship to each other, and forming with them a unitary anode assembly. The mounting members 3 are secured to the electrode faces adjacent one side of the electrode and extend substantially between the oppositely disposed sides of the electrode which are substantially perpendicular to the side at which the mounting members are secured.

The mounting members 3 extend from the electrode faces 9 and are substantially perpendicular thereto. The mounting members may be of various configurations. As is shown in the figures of the drawing, the mounting members are of a substantially L-shaped configuration, with oppositely disposed mounting members being secured to each other, preferably by welding, to form a substantially U-shaped member which maintains the desired spacing between the electrodes 1. Thus, in this configuration, the mounting members 3 on each electrode face extend from the face a distance which is approximately onehalf of the desired distance between the two adjacent electrodes.

Although this L-shaped configuration for the mounted members is particularly preferred, in that it is relatively easy to fabricate, other configurations may also be used. For example, the mounting members 3 may be a single U-shaped member which is secured to the opposite faces of two adjacent electrodes, rather than being formed of two L-shaped members. Similarly, the mounting member may be T-shaped, in which the top of the T is secured to the electrode face and the base of two adjoining Ts are secured together; H-shaped with the legs of the Hs secured to the faces of adjacent electrodes; as well as various other shapes, as will be apparent to those of ordinary skill in the art, including double-walled configuration of the wall of the electrolytic cell which is be a square, rectangle, circle, oval, or the like. The particular shape of the mounting member 3 which is used in each instance will depend upon the desired configuration of the wall of the electrolytic cell which is formed by these members in the complete assembly, as well as on the method of fabrication which is used.

In addition to the mounting members 3, end mounting members 7 are also provided, secured to the face of the two end electrodes in the assembly. This end mounting member 7 functions to secure the final anode assembly in the electrolytic cell in which the assembly is to be used. In the embodiment illustrated in FIGS. 1 and 2, this end mounting member has been shown as having the same configuration as the other mounting members 3. Other configurations may be used, however, depending upon the particular electrolytic cell and the manner in which the anode assembly is to be mounted therein. The end mounting members 7, as shown, are particularly adapted for mounting the anode assembly in a side entry or side mounted type of electrolytic cell, the mounting members 3 forming one side wall of the cell and the end mounting member 7 being secured to the two end walls of the boxcell structure.

The present anode assembly is further provided with electrical connecting means, which electrical connecting means are shown as a series of holes in the electrode, adjacent the mounting members. The form of these electrical connections may also be varied, as will be apparent to those in the art, to provide means whereby the external source of electrical current may be introduced into the anode assembly. The electrical connection means are positioned on the anode assembly such that they are adjacent to the mounting members, but on that side of the mounting members which will be external of the electrolytic cell. In this manner, the conventional busbars may be connected to the electrode by means of bolts inserted in the holes 5, without the need for various liquid sealing I means as has heretofore been necessary in cells in which electrical connections must pass into the interior of the cell. It is, therefore, seen that since the mounting members 3 form one wall of the electrolytic cell, it is important that the configuration chosen for these mounting members be such that, in combination with the particular type of electrical connection means used, the positioning of this connection means external of the cell is possible.

It is to be appreciated that although the present anode assembly have been shown in the drawing as being composed of only four electrodes, this is merely exemplary of the number of electrodes which may be used. Obviously, additional electrodes and mounting members may be provided, depending upon the particular size and capacity of the electrolytic cell which is desired. In this regard, it has been found that because of the rigidity imparted to the anode assembly, the cells having a capacity as high as 150,000 amps or higher, are quite feasible, particularly when using the preferred electrode construction as has been described above, and that such cells may be designed so that they do not occupy appreciably greater floor space than do many present cells of only a half to one-third of this capacity. Thus, not only are savings realized because of the simplicity of fabrication of these anode assemblies, but, additionally, there are appreciable savings in both operating costs and overall capital investment for an electrolytic cell installation.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. An anode assembly, suitable for use in a cell for the electrolysis of alkali halide solutions which comprises (1) a plurality of substantially parallelly disposed, plate-like electrodes, each of which have a pair of substantially parallel, plate-like faces, said electrodes having an outer surface of a valve metal selected from titanium, tantalum and niobium, coated with an electrically active material selected from noble metals, noble metal alloys, noble metal oxides and mixtures thereof, said noble metal being selected from platinum, palladium, ruthenium, rhodium and iridium, and an inner core of a material which is more electrically conductive than the valve metal of which said outer surface is formed, said inner core being completely encapsulated within said valve metal, each of said electrodes having two sets of substantially oppositely disposed sides,

(2) a plurality of mounting members, said mounting members being formed of a valve metal and being disposed between said electrodes and secured only to the oppositely disposed faces of adjacent electrodes at a point adjacent one side of one of said sets of sides of said electrode and extending between the two oppositely disposed sides of said other set of sides, that portion of said mounting member between said oppositely disposed faces of adjacent electrodes being substantially perpendicular to the electrode faces and being recessed from the side of the electrode to which the mounting member is secured so that a portion of said electrode extends beyond the perpendicularly disposed portion of said mounting members, said mounting members maintaining said electrodes in a substantially parallel relationship and forming with said electrodes a unitary anode assembly which forms one exterior wall of an electrolytic cell and (3) electrical connection means on each of said electrodes, said connection means being positioned in that portion of the electrode which extends beyond the perpendicularly disposed portion of the mounting member on the exterior side of the cell wall formed by the anode assembly, and said connection means further being formed so as to permit a direct connection of a busbar to said electrode, which direct connection is external of the cell.

2. The anode assembly as claimed in claim 1 in which there are a plurality of said mounting members, one of which is secured to each face of each electrode at a point adjacent one side of one of said sets of sides and extending between the two oppositely disposed sides of the other set, said mounting members each being substantially perpendicular to the face of the electrode to which it is secured and extending therefrom a distance which is about onehalf the desired distance between two adjacent electrodes in the final electrode assembly, said mounting members on the face of one electrode being secured to the corre- 7 8 sponding mounting member on the face of an adjacent References Cited electrode so as to form the unitary anode assembly. UNITED STATES PATENTS 3. The anode assembly as claimed in claim 2 wherein the inner core of the electrode is aluminum, the outer sur- 3,133,872 5/1964 M111 et F face of the electrode is titanium, and the coating of the 5 FO GN PATENTS 315121132213 6 active material on the titamum contains ruthe- 318,734 9/1929 Great Britain 204258 1,125,493 8/1968 Great Britain 204266 4. The anode assembly as claimed in claim 3 wherein the mounting members are formed of the same valve metal as the electrode.

5. The anode assembly as claimed in claim 4 wherein the mounting members are substantially L-shaped in cross section.

6. The anode assembly as claimed in claim 5 wherein the mounting members are secured to the electrode faces 15 and to each other by welding.

1,127,484 9/1968 Great Britain 204266 FREDERICK c. EDMUNDSON, Primary Examiner US. Cl. X.R. 204286, 289 

